The present invention relates to railroad track maintenance equipment and more particularly to a stoneblower workhead and blowing tubes.
Stoneblowers are used in the maintenance of railroad track to blow ballast stones beneath track sleepers or ties and raise the track to a desired elevation. Such stoneblowers are a wheeled car having a superstructure carrying a track lifting device, a supply of ballast stones, a source of compressed air, and a number of workheads. Each workhead carries a pair of blowing tubes. In operation, the track lifting device raises the track rails and the ties to which the rails are secured. The workhead forces the blowing tubes into the ballast adjacent the raised track ties with each pair of blowing tubes straddling a rail. Stone is then blown through the blowing tubes into the voids beneath the raised ties. The workhead withdraws the blowing tubes and the track is lowered. The stoneblower then advances to the next ties and repeats this procedure.
Blowing tubes are formed with vertically elongated end openings through which the stone exits. It is desirable to position the blowing tubes as close as possible to the ties such that the upper extents of the openings are effectively sealed against the ties, thus allowing stone to exit only beneath the tie. However, the exit opening below the tie can result in a clogged blowing tube when there is stone overflow. Some blowing tubes are provided with a second opening above the tie face to allow stone to overflow in the event the exit opening becomes clogged.
Stoneblowers have been provided with workhead mountings that allow the workheads to be moved longitudinally with respect to the superstructure and the track rails, thus allowing the blowing tubes to be positioned near the leading and trailing faces of the ties before the tubes are inserted into the ballast. Longitudinal adjustability of the stoneblower workheads is useful to allow a degree of tolerance in the placement of the superstructure over the ties and to compensate for variations in the spacing of the ties. However, longitudinal adjustability alone does not compensate for angular skewing of the ties or for ties having nonvertical leading or trailing faces. If a tie is not perpendicular to the rails, it is not possible to position both of the blowing tubes on a single workhead close against the face of the tie. If the tie has a trapezoidal cross section, as is usual with cast concrete ties, a gap exists between the upper extent of the face of the tie and the blowing tube opening.
In the past, blowing tubes have been formed from metal tubes of pipes. The stone exit openings of the blowing tubes have been formed by cutting a longitudinal slit through the tube wall and a circumferential cut at the upper end of the slit. The tube wall is then bent outwardly along either side of the slit. This creates an abrupt transition in the shape of the tube at the upper end of the exit opening. The abrupt transition creates a stress riser making the tube susceptible to cracking and damage at the transition.